Deployment of Herbicide Ballistic Technology (HBT) in Hawaii: A case study on eliminating incipient invasive species targets with extreme prejudice

James Leary, Assistant Professor

Learning Outcomes:

• Uniqueness of Hawaii

• Biology and life history traits of a

tropical invasive plant species

• Concepts in aerial surveillance with

manned helicopter operations

• GIS analyses of operations data

• Bioeconomics of controlling an invasive

species

:

1,400 native plants in 5M yr

30 canoe plants in 2K yr

>10,000 introduced plants in 200 yr

Invasion History of Hawaii

• 90% of native species are endemic

• >10,000 introduced plants

• ~200 disruptive invasive species ecosystems and natural resources

Hawaii the Endangered/Invasive Species Capital of the World

Life History Traits of

Miconia (Miconia calvescens DC)

• An autogamous (self-fertile) species

• High fecundity

• Edible to broad range of frugivores

• Long dispersal range

• Persistent seed viability

• Germination in heavy shade

Meyer 1998, Murphy et al. 2008

Photo: F. Starr

East Maui Watershed (eastmauiwatershed.org):150,000 acres from sea level to 10,023′ a.s.l.

Critical habitat for over 100 threatened and endangered species

Annually produces 60 billion gallons of fresh surface water

(Largest single source of water in the State of Hawaii)

Miconia purposely introduced

as botanical specimen (founder

population)

Invasion History of Miconia in the East Maui Watershed

ca. 1970

Invasion History of Miconia in the East Maui Watershed

2011 (n=981,630)

Core infestation >2000 acres

Invasion spread across 30% of

the EMW

Herbicide Ballistic Technology (HBT) targeting Miconia (Miconia calvescens)

Photo: J. Atwood

Herbicide Ballistic Technology (HBT)

Problem: Incipient populations of miconia are colonizing remote sections of class I

watersheds on Maui. Average slope of terrain >50% >>> AREAS INACCESSIBLE TO GROUND

MANAGEMENT

Concept: Encapsulated 0.68 caliber herbicide-filled projectiles pneumatically delivered to

treat isolated plant populations >>> LONG DISTANCE ACCURACY (20-30 m) WITH FULL TILT

TRAJECTORY (0-90O)

Objective: Detect and eliminate incipient populations

0.68 caliber soft gel projectiles

encapsulating 200 mg triclopyr

HBT SD heliops

HBT operations conducted with a Hughes 500D helicopter

Payload Operator “Applicator” portside behind Pilot with shared 8-12 o’clock field of view (FOV)

Navigator front-starboard for 12-3 o’clock FOV and hazard awareness

Contour surveillance:

Low alt agl (≤30 m) at slow search speeds (10 knots)

Operational flight time 80-90 min per cycle

Scan rate is ~0.5 sec pixel-1 (100 m2)

Invasion History of Miconia in the East Maui Watershed

1991-2011 (n=981,630)

HBT 2012-2018 (n=25,956; yellow)

y = 39.588x + 83.657R² = 0.6266

0

100

200

300

400

500

600

0 2 4 6 8

sec

ha-1

Target ha-1

Variable costs of HBT operations determined by target density

$24.90 ha-1 and $20.71 tgt-1

• Search effort is a linear function of target density with search effort (EFT; y-intercept)

equal to 83 sec ha-1 = $24.90 and target engage equal to 40 sec tgt-1 = $12.00

• Herbicide use rate is also a linear function of target density with average dose (slope)

equal to 4.28 g ae (~22 projectiles) = $6.71

y = 4.2753xR² = 0.8126

0

10

20

30

40

0 2 4 6 8

Gra

ms

ae h

a-1Target ha-1

Search Effort Herbicide Use Rate

Propagule Dispersal and Persistence Kernels of Miconia

• Near analyses calculating the distance and time interval of progeny to maternal source.

• Dispersal kernels are leptokurtic with 99% of progeny within 587 m of the maternal source

and rare long-distance events out to 1640 m.

• Seed bank depletion 90% in <10 yrs; extinction estimated between 20-30 years

• These estimates are highly congruent to dispersal estimates in AU (Fletcher and Westcott

2013) and seed bank longevity in Tahiti (Meyer 2010)

Dispersal Recruitment

0

0.1

0.2

0.3

0 600 1200 1800

Pro

gen

y P

rop

ort

ion

Dispersal Range (m)

0.0

0.2

0.4

0.6

0.8

1.0

0 5 10 15 20

Pro

gen

y P

rop

ort

ion

Years after Reproduction

Spatial Impact and Future Cost of an Incipient Miconia Colonizing New Range

• Maximum dispersal distance creates an impact area >2000 acres

• >90% of total cost searching for 1% of targets

• The highest recruit densities cost >$300 pixel-1; effective search is $0.42 pixel-1

• The total estimated cost $42K to eradicate a new incipient population

0.01 tgt

y = $20.71x + $0.42

0

90

180

270

360

0481216

Co

st (

$ U

SD)

Targets Pixel-1

Dispersal kernel Density cost spectrum

• Only ~12% of impacted area (grey) surveyed (i.e., protected)

• >50% of mature plants detected on the first intervention (reconnaissance)

• Time between interventions is 2x longer for mature detection i.e., 180 days

Search freq.ReconnaissanceSearch effort

Management to Achieve Containment

2012-2018 We’ve invested over $799K, conducting 157 HBT operations:

Eliminating 25,956 incipient targets Protecting 17,433 ha of watershed Avoiding $1.1 B in future management costs

2012-2018 We’ve invested over $799K, conducting 157 HBT operations:

Eliminating 294 incipient MATURE targets Impacting 14,670 ha of watershed Adding min. $12.2 M in future management costs

98.9% effective!?!

Review of concepts:

• Knowledge of phenology, fecundity

and dispersal enhances our capacity

to measure impact on the landscape

and project long-term strategies

• GPS records of the area searched and

for every target treated offers the

most accurate cost assessment

• Operational cost is density dependent

• The most economical form of

management is searching and not

finding

Thank you very much.

Questions?